A large variety of liquid products such as those mentioned above and even some solid products are commercialized in plastic bags, hermetically sealed, which keep the contents protected from the surroundings. At other times, plastified cardboard containers are used such as the well-known "tetra-brik". Usually when this type of container is used, in order to consume the product, an oblique cut is made at the corner of the carton thus forming an opening through which the contents may be poured out. This opening usually measures between 1 and 2 cm. although in some cases it may measure more or less.
This type of container poses a two-fold problem. On the one hand, once the carton is opened, the contents run the risk of deteriorating and on the other hand, because of the flexible nature of the carton itself, there exists the likelihood of the contents being spilt while handling the carton.